Time mating guinea pigs by monitoring changes to the vaginal membrane throughout the estrus cycle and with ultrasound confirmation

One of the greatest challenges to the development and implementation of pregnancy therapeutics is the ability to rigorously test treatments in clinically relevant animal models. Guinea pigs offer a unique advantage in studying the placenta, fetal development, and reproductive health as they have similar developmental milestones to humans, both throughout gestation and following birth. Tracking the guinea pig estrus cycle is imperative to ensuring appropriately timed mating and can be performed by monitoring the guinea pig vaginal membrane. Here, we describe a methodology to efficiently and accurately time mate guinea pigs, and provide a picture representation of changes to the guinea pig vaginal membrane throughout the estrus cycle. Utilization of this monitoring enabled a 100% pregnancy success rate on the first mating attempt in a cohort of five guinea pigs. This approach, along with early pregnancy ultrasounds as a secondary method to confirm pregnancy, offers a reliable approach to timed mating in the guinea pig

Representative diatom and coccolithophore species exhibit divergent responses throughout simulated upwelling cycles

Wind-driven upwelling followed by relaxation results in cycles of cold nutrient- rich water fueling intense phytoplankton blooms followed by nutrient depletion, bloom decline, and sinking of cells. Surviving cells at depth can then be vertically transported back to the surface with upwelled waters to seed another bloom. As a result of these cycles, phytoplankton communities in upwelling regions are transported through a wide range of light and nutrient conditions. Diatoms appear to be well suited for these cycles, but their responses to them remain understudied. To investigate the bases for diatoms' ecological success in upwelling environments, we employed laboratory simulations of a complete upwelling cycle with a common diatom, Chaetoceros decipiens, and coccolithophore, Emiliania huxleyi. We show that while both organisms exhibited physiological and transcriptomic plasticity, the diatom displayed a distinct response enabling it to rapidly shift-up growth rates and nitrate assimilation when returned to light and available nutrients following dark nutrient-deplete conditions. As observed in natural diatom communities, C. decipiens highly expresses before upwelling, or frontloads, key transcriptional and nitrate assimilation genes, coordinating its rapid response to upwelling conditions. Low-iron simulations showed that C. decipiens is capable of maintaining this response when iron is limiting to growth, whereas E. huxleyi is not. Differential expression between iron treatments further revealed specific genes used by each organism under low iron availability. Overall, these results highlight the responses of two dominant phytoplankton groups to upwelling cycles, providing insight into the mechanisms fueling diatom blooms during upwelling events

Strategies among phytoplankton in response to alleviation of nutrient stress in a subtropical gyre

Despite generally low primary productivity and diatom abundances in oligotrophic subtropical gyres, the North Atlantic Subtropical Gyre (NASG) exhibits significant diatom-driven carbon export on an annual basis. Subsurface pulses of nutrients likely fuel brief episodes of diatom growth, but the exact mechanisms utilized by diatoms in response to these nutrient injections remain understudied within near-natural settings. Here we simulated delivery of subsurface nutrients and compare the response among eukaryotic phytoplankton using a combination of physiological techniques and metatranscriptomics. We show that eukaryotic phytoplankton groups exhibit differing levels of transcriptional responsiveness and expression of orthologous genes in response to release from nutrient limitation. In particular, strategies for use of newly delivered nutrients are distinct among phytoplankton groups. Diatoms channel new nitrate to growth-related strategies while physiological measurements and gene expression patterns of other groups suggest alternative strategies. The gene expression patterns displayed here provide insights into the cellular mechanisms that underlie diatom subsistence during chronic nitrogen-depleted conditions and growth upon nutrient delivery that can enhance carbon export from the surface ocean

Marine snow formation by the toxin-producing diatom, Pseudo-nitzschia australis

The formation of marine snow (MS) by the toxic diatom Pseudo-nitschia australis was simulated using a roller table experiment. Concentrations of particulate and dissolved domoic acid (pDA and dDA) differed significantly among exponential phase and MS formation under simulated near surface conditions (16 °C/12:12-dark:light cycle) and also differed compared to subsequent particle decomposition at 4 °C in the dark, mimicking conditions in deeper waters. Particulate DA was first detected at the onset of exponential growth, reached maximum levels associated with MS aggregates (1.21 ± 0.24 ng mL−1) and declined at an average loss rate of ∼1.2% pDA day−1 during particle decomposition. Dissolved DA concentrations increased throughout the experiment and reached a maximum of ∼20 ng mL−1 at final sampling on day 88. The succession by P. australis from active growth to aggregation resulted in increasing MS toxicity and based on DA loading of particles and known in situ sinking speeds, a significant amount of toxin could have easily reached the deeper ocean or seafloor. MS formation was further associated with significant dDA accumulation at a ratio of pDA: dDA: cumulative dDA of approximately 1:10:100. Overall, this study confirms that MS functions as a major vector for toxin flux to depth, that Pseudo-nitzschia-derived aggregates should be considered ‘toxic snow’ for MS-associated organisms, and that effects of MS toxicity on interactions with aggregate-associated microbes and zooplankton consumers warrant further consideration

The iron limitation mosaic in the California Current System: Factors governing Fe availability in the shelf/near-shelf region

The California Current System is a productive eastern boundary region off the coasts of Washington, Oregon, and California. There is strong seasonality to the region, with high levels of rainfall and river input to the coastal ocean during the winter season, and coastal and Ekman upwelling during the spring and summer. Iron (Fe) input to the coastal ocean during the winter months can be stored in the continental shelf mud belts and then be delivered to the surface ocean by upwelling in the spring and summer. There have been a number of studies providing strong evidence of Fe-limitation of diatom growth occurring in regions of the California Current System off of California, and the occurrence of Fe-limitation has been linked with narrow continental shelf mud belt width and low river input. We provide evidence for potential Fe-limitation of diatoms off the southern coast of Oregon in July 2014, just off the shelf break near Cape Blanco in a region with moderate shelf width and river input. Since eastern boundary regions account for a disproportionally large amount of global primary production, this observation of potential Fe-limitation in an unexpected near-shore region of the California Current System has implications for global models of primary productivity. In order to re-evaluate the factors impacting Fe availability, we utilize satellite imagery to compare with historical datasets, and show that unexpected levels of Fe can often be explained by eddies, plumes of upwelled water moving offshore, or lack of recent upwelling

Development of a molecular-based index for assessing iron status in bloom-forming pennate diatoms

Iron availability limits primary productivity in large areas of the world's oceans. Ascertaining the iron status of phytoplankton is essential for understanding the factors regulating their growth and ecology. We developed an incubation-independent, molecular-based approach to assess the iron nutritional status of specific members of the diatom community, initially focusing on the ecologically important pennate diatom Pseudo-nitzschia. Through a comparative transcriptomic approach, we identified two genes that track the iron status of Pseudo-nitzschia with high fidelity. The first gene, ferritin (FTN), encodes for the highly specialized iron storage protein induced under iron-replete conditions. The second gene, ISIP2a, encodes an iron-concentrating protein induced under iron-limiting conditions. In the oceanic diatom Pseudo-nitzschia granii (Hasle) Hasle, transcript abundance of these genes directly relates to changes in iron availability, with increased FTN transcript abundance under iron-replete conditions and increased ISIP2a transcript abundance under iron-limiting conditions. The resulting ISIP2a:FTN transcript ratio reflects the iron status of cells, where a high ratio indicates iron limitation. Field samples collected from iron grow-out microcosm experiments conducted in low iron waters of the Gulf of Alaska and variable iron waters in the California upwelling zone verify the validity of our proposed Pseudo-nitzschia Iron Limitation Index, which can be used to ascertain in situ iron status and further developed for other ecologically important diatoms

Iron and vitamin interactions in marine diatom isolates and natural assemblages of the Northeast Pacific Ocean

Trace metals and B-vitamins play critical roles in regulating marine phytoplankton growth and composition. While some microorganisms are capable of producing certain B-vitamins, others cannot synthesize them and depend on an exogenous supply. Therefore, external factors influencing vitamin synthesis, such as micronutrient concentrations, alter the extent to which B-vitamins are available to auxotrophs in surface waters. We examined iron, B7 (biotin) and B12 (cobalamin) dynamics in diatoms through laboratory culture experiments and within natural diatom assemblages present along an iron gradient in the Northeast Pacific Ocean. In laboratory cultures of the diatom Pseudo-nitzschia granii, biotin synthase (BIOB) expression decreased 2-fold under iron limitation, suggesting iron status may affect B7 production in diatoms. Additionally in laboratory cultures of the diatom Grammonema cf. islandica, which contains a B12-independent methionine synthase (METE), a 15-fold increase in the expression of METE was observed when grown in the absence of B12 with no significant influence of iron status, suggesting METE expression can be driven by B12 status alone. Iron and B-vitamin amendment experiments with natural diatom assemblages in iron-limited waters of the Northeast Pacific Ocean provide evidence for vitamin-associated molecular responses that suggest elevated B7 biosynthesis and the emergence of B12 limitation following iron addition. Furthermore B-vitamin gene modules comprised of partial and/or complete B-vitamin biosynthetic pathways in diatoms increased in response to iron addition, including genes potentially involved in the processing of B12 intermediates. Our results indicate that vitamins may play an important role in regulating phytoplankton growth and composition in this region, particularly following natural iron addition events

Impaired viral infection and reduced mortality of diatoms in iron-limited oceanic regions

Diatom primary productivity is tightly coupled with carbon export through the ballasted nature of the silica-based cell wall, linking the oceanic silicon and carbon cycles. However, despite low productivity, iron (Fe)-limited regimes are considered ‘hot spots’ of diatom silica burial with enhanced carbon export efficiency, raising questions about the mechanisms driving the biogeochemistry of these regions. Marine viruses are classically recognized as catalysts of remineralization through host lysis, short-circuiting the trophic transfer of carbon and facilitating the retention of dissolved organic matter and associated elements in the surface ocean. Here we used metatranscriptomic analysis of diatoms and associated viruses, along with a suite of physiological and geochemical metrics, to study the interaction between diatoms and viruses in Fe-limited regimes of the northeast Pacific. We found low cell-associated diatom virus diversity and abundance in a chronically Fe-limited region of the subarctic northeast Pacific. In a coastal upwelling region of the California Current, transient iron limitation also substantially reduced viral replication. These observations were recapitulated in Fe-limited cultures of the bloom-forming, centric diatom, Chaetoceros tenuissimus, which exhibited delayed virus-mediated mortality in addition to reduced viral replication. We suggest Fe-limited diatoms escape viral lysis and subsequent remineralization in the surface ocean, providing an additional mechanism contributing to enhanced carbon export efficiency and silica burial in Fe-limited oceanic regimes

Divergent gene expression among phytoplankton taxa in response to upwelling

Frequent blooms of phytoplankton occur in coastal upwelling zones creating hotspots of biological productivity in the ocean. As cold, nutrient-rich water is brought up to sunlit layers from depth, phytoplankton are also transported upwards to seed surface blooms that are often dominated by diatoms. The physiological response of phytoplankton to this process, commonly referred to as shift-up, is characterized by increases in nitrate assimilation and rapid growth rates. To examine the molecular underpinnings behind this phenomenon, metatranscriptomics was applied to a simulated upwelling experiment using natural phytoplankton communities from the California Upwelling Zone. An increase in diatom growth following 5 days of incubation was attributed to the genera Chaetoceros and Pseudo-nitzschia. Here, we show that certain bloom-forming diatoms exhibit a distinct transcriptional response that coordinates shift-up where diatoms exhibited the greatest transcriptional change following upwelling; however, comparison of co-expressed genes exposed overrepresentation of distinct sets within each of the dominant phytoplankton groups. The analysis revealed that diatoms frontload genes involved in nitrogen assimilation likely in order to outcompete other groups for available nitrogen during upwelling events. We speculate that the evolutionary success of diatoms may be due, in part, to this proactive response to frequently encountered changes in their environment

Collider aspects of flavour physics at high Q

This review presents flavour related issues in the production and decays of heavy states at LHC, both from the experimental side and from the theoretical side. We review top quark physics and discuss flavour aspects of several extensions of the Standard Model, such as supersymmetry, little Higgs model or models with extra dimensions. This includes discovery aspects as well as measurement of several properties of these heavy states. We also present public available computational tools related to this topic.Comment: Report of Working Group 1 of the CERN Workshop ``Flavour in the era of the LHC'', Geneva, Switzerland, November 2005 -- March 200